Spring Cloud Gateway网关实战及原理解析

API 网关

API 网关出现的原因是微服务架构的出现，不同的微服务一般会有不同的网络地址，而外部客户端可能需要调用多个服务的接口才能完成一个业务需求，如果让客户端直接与各个微服务通信，会有以下的问题：

• 客户端会多次请求不同的微服务，增加了客户端的复杂性。
• 存在跨域请求，在一定场景下处理相对复杂。
• 认证复杂，每个服务都需要独立认证。
• 难以重构，随着项目的迭代，可能需要重新划分微服务。例如，可能将多个服务合并成一个或者将一个服务拆分成多个。如果客户端直接与微服务通信，那么重构将会很难实施。
• 某些微服务可能使用了防火墙 / 浏览器不友好的协议，直接访问会有一定的困难。

以上这些问题可以借助 API 网关解决。API 网关是介于客户端和服务器端之间的中间层，所有的外部请求都会先经过 API 网关这一层。也就是说，API 的实现方面更多的考虑业务逻辑，而安全、性能、监控可以交由 API 网关来做，这样既提高业务灵活性又不缺安全性，典型的架构图如图所示：

使用 API 网关后的优点如下：

• 易于监控。可以在网关收集监控数据并将其推送到外部系统进行分析。
• 易于认证。可以在网关上进行认证，然后再将请求转发到后端的微服务，而无须在每个微服务中进行认证。
• 减少了客户端与各个微服务之间的交互次数。

API 网关选型

业界的情况：

 

我前面的文章<Netflix网关zuul(1.x和2.x)全解析>已经介绍了zuul1 和zuul2，现在就尝试从实例入手介绍一下spring cloud gateway

首先我们一步步实现一个最简单的网关例子

步骤1：在http://start.spring.io网站上创建一个spring-cloud-gateway-example项目，依赖spring-cloud-gateway，如下图所示

 

此时生产了一个spring-cloud-gateway-example的空项目包，pom.xml文件如下

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<? xml version = "1.0" encoding = "UTF-8" ?>< project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 [url]http://maven.apache.org/xsd/maven-4.0.0.xsd[/url]" >    < modelVersion >4.0.0</ modelVersion >    < parent >        < groupId >org.springframework.boot</ groupId >        < artifactId >spring-boot-starter-parent</ artifactId >        < version >2.1.3.RELEASE</ version >        < relativePath /> <!-- lookup parent from repository -->    </ parent >    < groupId >com.example</ groupId >    < artifactId >spring-cloud-gateway-example</ artifactId >    < version >0.0.1-SNAPSHOT</ version >    < name >spring-cloud-gateway-example</ name >    < description >Demo project for Spring Boot</ description >    < properties >        < java.version >1.8</ java.version >        < spring-cloud.version >Greenwich.RELEASE</ spring-cloud.version >    </ properties >    < dependencies >        < dependency >            < groupId >org.springframework.cloud</ groupId >            < artifactId >spring-cloud-starter-gateway</ artifactId >        </ dependency >        < dependency >            < groupId >org.springframework.boot</ groupId >            < artifactId >spring-boot-starter-test</ artifactId >            < scope >test</ scope >        </ dependency >    </ dependencies >    < dependencyManagement >        < dependencies >            < dependency >                < groupId >org.springframework.cloud</ groupId >                < artifactId >spring-cloud-dependencies</ artifactId >                < version >${spring-cloud.version}</ version >                < type >pom</ type >                < scope >import</ scope >            </ dependency >        </ dependencies >    </ dependencyManagement >    < build >        < plugins >            < plugin >                < groupId >org.springframework.boot</ groupId >                < artifactId >spring-boot-maven-plugin</ artifactId >            </ plugin >        </ plugins >    </ build >    < repositories >        < repository >            < id >spring-milestones</ id >            < name >Spring Milestones</ name >            < url >[url]https://repo.spring.io/milestone</ url >[/url]        </ repository >    </ repositories ></ project >[url=]

 

2.创建一个Route实例的配置类GatewayRoutes

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package com.example.springcloudgatewayexample; import org.springframework.cloud.gateway.route.RouteLocator; import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configurationpublic class GatewayRoutes {    @Bean    public RouteLocator routeLocator(RouteLocatorBuilder builder) {        return builder.routes()                .route(r ->                        r.path( "/java/**" )                                .filters(                                        f -> f.stripPrefix( 1 )                                )                                .uri( "http://localhost:8090/helloWorld" )                )                .build();    }}

 

当然，也可以不适用配置类，使用配置文件，如下图所示

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1	spring:  cloud:    gateway:      routes:         - predicates:            - Path=/java/**          filters:            - StripPrefix= 1          uri: "http://localhost:8090/helloWorld"

不过，为了调试方便，我们使用配置类方式。

此时项目已经完成，足够简单吧。

3.启动此项目

  >>因api网关需要转发到一个服务上，本文为http://localhost:8090/helloWorld，那需要先启动我上文<spring boot整合spring5-webflux从0开始的实战及源码解析>,你也可以创建一个普通的web项目，启动端口设置为8090，然后启动。

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. ____ _ __ _ _/\\ / ___ '_ __ _ _(_)_ __ __ _ \ \ \ \( ( )\___ | ' _ | '_| | ' _ \/ _` | \ \ \ \\\/ ___)| |_)| | | | | || (_| | ) ) ) )' |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/= /_/_/_/ :: Spring Boot :: (v2.1.3.RELEASE)2019-02-21 09:29:07.450 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : Starting Spring5WebfluxApplication on DESKTOP-405G2C8 with PID 11704 (E:\workspaceForCloud\spring5-webflux\target\classes started by dell in E:\workspaceForCloud\spring5-webflux)2019-02-21 09:29:07.455 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : No active profile set , falling back to default profiles: default2019-02-21 09:29:09.409 INFO 11704 --- [ main] o.s.b.web.embedded.netty.NettyWebServer : Netty started on port(s): 80902019-02-21 09:29:09.413 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : Started Spring5WebfluxApplication in 2.304 seconds (JVM running for 7.311)

>>以spring boot方式启动spring-cloud-gateway-example项目，日志如下

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2019-02-21 10:34:33.435  INFO 8580 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$1e059320] is not eligible for getting processed by all BeanPostProcessors ( for example: not eligible for auto-proxying)  .   ____          _            __ _ _ /\\ / ___ '_ __ _ _(_)_ __  __ _ \ \ \ \( ( )\___ | ' _ | '_| | ' _ \/ _` | \ \ \ \ \\/  ___)| |_)| | | | | || (_| |  ) ) ) )  '  |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot ::        (v2.1.3.RELEASE)2019-02-21 10:34:33.767  INFO 8580 --- [           main] e.s.SpringCloudGatewayExampleApplication : No active profile set, falling back to default profiles: default2019-02-21 10:34:34.219  INFO 8580 --- [           main] o.s.cloud.context.scope.GenericScope     : BeanFactory id=d98183ec-3e46-38ba-ba4c-e976a1017dce2019-02-21 10:34:34.243  INFO 8580 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean ' org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$1e059320] is not eligible for getting processed by all BeanPostProcessors ( for example: not eligible for auto-proxying)2019-02-21 10:34:44.367  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [After]2019-02-21 10:34:44.367  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Before]2019-02-21 10:34:44.367  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Between]2019-02-21 10:34:44.367  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Cookie]2019-02-21 10:34:44.367  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Header]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Host]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Method]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Path]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Query]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [ReadBodyPredicateFactory]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [RemoteAddr]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Weight]2019-02-21 10:34:44.368  INFO 8580 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [CloudFoundryRouteService]2019-02-21 10:34:44.920  INFO 8580 --- [           main] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port(s): 80802019-02-21 10:34:44.923  INFO 8580 --- [           main] e.s.SpringCloudGatewayExampleApplication : Started SpringCloudGatewayExampleApplication in 12.329 seconds (JVM running for 13.126)

4.测试，浏览器访问http://localhost:8080/java/helloWorld

返回hello world ！

5.从上面的代码和配置及实例中，我们可以看出spring cloud gateway处理request请求的流程如下所示：

 

即在最前端，启动一个netty server（默认端口为8080）接受请求，然后通过Routes（每个Route由Predicate(等同于HandlerMapping)和Filter(等同于HandlerAdapter)）处理后通过Netty Client发给响应的微服务。

那么在gateway本身最重要的应该是Route（Netty Server和Client已经封装好了），它由RouteLocatorBuilder构建，内部包含Predicate和Filter，

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1	private Route(String id, URI uri, int order, AsyncPredicate<ServerWebExchange> predicate, List<GatewayFilter> gatewayFilters) {        this .id = id;        this .uri = uri;        this .order = order;        this .predicate = predicate;        this .gatewayFilters = gatewayFilters;    }

那么我们就来探讨一下这两个组件吧

5.1.Predicate

Predicte由PredicateSpec来构建，主要实现有：

 

以path为例

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/**     * A predicate that checks if the path of the request matches the given pattern     * @param patterns the pattern to check the path against.     *                The pattern is a {@link org.springframework.util.PathMatcher} pattern     * @return a {@link BooleanSpec} to be used to add logical operators     */    public BooleanSpec path(String... patterns) {        return asyncPredicate(getBean(PathRoutePredicateFactory. class )                .applyAsync(c -> c.setPatterns(Arrays.asList(patterns))));    }

 

PathRoutePredicateFactory中执行

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@Override    public Predicate<ServerWebExchange> apply(Config config) {        final ArrayList<PathPattern> pathPatterns = new ArrayList<>();        synchronized ( this .pathPatternParser) {            pathPatternParser.setMatchOptionalTrailingSeparator(                    config.isMatchOptionalTrailingSeparator());            config.getPatterns().forEach(pattern -> {                PathPattern pathPattern = this .pathPatternParser.parse(pattern);                pathPatterns.add(pathPattern);            });        }        return exchange -> {            PathContainer path = parsePath(exchange.getRequest().getURI().getPath());            Optional<PathPattern> optionalPathPattern = pathPatterns.stream()                    .filter(pattern -> pattern.matches(path)).findFirst();            if (optionalPathPattern.isPresent()) {                PathPattern pathPattern = optionalPathPattern.get();                traceMatch( "Pattern" , pathPattern.getPatternString(), path, true );                PathMatchInfo pathMatchInfo = pathPattern.matchAndExtract(path);                putUriTemplateVariables(exchange, pathMatchInfo.getUriVariables());                return true ;            }            else {                traceMatch( "Pattern" , config.getPatterns(), path, false );                return false ;            }        };    }

5.2.Filter

Filter分两种，一种GatewayFilter,一种GlobalFilter

5.2.1 GatewayFilter

GatewayFilter由GatewayFilterSpec构建，GatewayFilter的构建器

 

5.2.2 GlobalFilter

 

5.3 GlobalFilter和GatewayFilter的联系

FilteringWebHandler.GatewayFilterAdapter代理了GlobalFilter

6.总结

  本文从一个spring-cloud-gateway实例入手，深入浅出的介绍了spring-cloud-gateway的组件，并从源码角度给出了实现的原理。

   spring-cloud-gateway在最前端，启动一个netty server（默认端口为8080）接受请求，然后通过Routes（每个Route由Predicate(等同于HandlerMapping)和Filter(等同于HandlerAdapter)）处理后通过Netty Client发给响应的微服务。

Predicate和Filter的各个实现定义了spring-cloud-gateway拥有的功能。

参考资料：

【1】https://www.infoq.cn/article/comparing-api-gateway-performances

【2】https://dzone.com/articles/sprin ... ring-a-simple-route